GB2146530A - Pesticide dispenser - Google Patents

Abstract

A device for pesticidal protection on a surface,which comprises a coherent solid source of pesticide comprising an absorbent solid impregnated with a pesticide e.g. a pyrethroid, said source being contained within a wrapping or holder adapted to be manipulated progressively to expose said source, and said source being such that when the so exposed part thereof is drawn across a surface small particles thereof will be detached therefrom and transferred to said surface to form a coherent band of particles thereon, said particles comprising absorbent solid and pesticide.

Description

SPECIFICATION Pesticide dispenser, and a method of providing pesticidal protection for surfaces The present invention is concerned with a dispenser for applying pesticides to surfaces, and with a method of providing pesticidal protection by the controlled application of a pesticide to a surface.

It is known to apply pesticides in admixture with solid diluents or carriers in pelleted or finely-divided, dry particulate form in order to facilitate distribution. For example, a powdered composition comprising a solid carrier and a pesticide can be dispensed from a "puffer" pack and dusted onto a floor or a window ledge.

This is an instance in which powdered compositions can be used to provide a source of pesticide which will be effective for an appreciable period providing the powder remains in the location to which it has been applied. Such compositions are formulated from solids which are readily and cheaply available in a sufficiently finely-divided form, and which are capable of absorbing an effective amount of pesticide. They are quite suitable for controlling insects and other pests in buildings. However, the use of such powdered compositions, and also compositions in which the particulate solid component is of larger size such as granules, has certain disadvantages and limitations.Among the disadvantages are the visual effect of the applied composition which one would prefer to avoid in many domestic building locations for example, and the fact that dusted on compositions are so easily removed by wind or inadvertently during routine cleaning.

An obvious limitation is that such powdered compositions cannot be used effectively on vertical surfaces because when simply dusted or blown on they do not cling to any substantial extent to the surface but only rest on it, and even if adequate "clinging power" could be imparted, the visual effect of a powdered material puffed over an appreciable area of a surface such as a window or wall would be unacceptable in the average domestic situation.

Further, the use of powdered materials can often cause environmental problems, since the powder can become airborne and be inhaled. This is a major problem inside buildings.

Much effort has been devoted in the artto devising sources of pesticides which can be placed in selected locations within buildings in order to combat pests. The nature of the pests encountered tends to be influenced by the geographical location of the buildings, for example in some countries the domestic fly may be the most common pest, whilst in others ants and cockroaches may require control. It is not easy to provide safe and effective sources of pesticide which will remain active for long periods, be relatively cheap and uncomplicated, and visually acceptable in domestic applications.

An important development in this area is disclosed in European Patent Specification No. 22592, which is concerned with a dispenser for applying a fluid or semi-fluid insecticide and/or fungicide formulation to a surface, the dispenser having an outlet orifice closed by a plug permeable to said formulation which in use of the dispenser is adapted to be drawn across a surface in frictional contact therewith so as to apply thereto a thin, relatively narrow band of the fluid or semi-fluid formulation. Such a dispenser represented an important development in the art since it is based on the discovery that effective pest control can be achieved by the application of such narrow bands of the formulation, a discovery which was surprising to those in the art.

The use of fluid or semi-fluid formulations has the advantage of ease of application and the fact that the protective band applied is so thin and narrow that it is virtually invisible, the amount of formulation used each time is so small that a pocket sized dispenser is a practical proposition, and the time taken to provide protection is minimal.

The Applicants have continued their investigations in the hope of devising a complementary dispenser which would be capable of applying a non-fluid pesticide formulation to surfaces for which a fluid formulation can have disadvantages, for example, the unsealed surface of a polyvinyl chloride tile can absorb certain pesticidal compounds which is bad for the tile and leads to loss of pesticide. A similar situation can arise with certain painted surfaces. A porous surface such as mortar, plywood or hardboard surface can also absorb such compounds leading to a loss of pesticide. Another requirement in certain circumstances is the ability to detect the thin, narrow band of formulation which has been applied so that occupants of a building can readily determine that protection has been provided.To incorporate a colourant in the formulation does not afford a practical solution because the colourant could persist after the pesticide component has been exhausted.

The Applicants have not succeeded in finding an analogous technique for directly applying a powdered pesticidal composition in band form. However, they have found, in accordance with the present invention, that a dispenser comprising a stick within a protective holder, the stick being formed by compaction of a powdered absorptive inorganic solid and incorporation within the solid phase of a pesticide, can be used in a similar manner to the dispenser of the aforesaid European Specification to provide a thin, relatively narrow band of pesticide-impregnated powder on a surface.

Accordingly the present invention provides a device suitable for providing pesticidal protection on a surface, which comprises a coherent solid source of pesticide comprising an absorbent solid impregnated with a pesticide, said source being contained within a wrapping or holder adapted to be manipulated progressively to expose said source, and said source being such that when the so exposed part thereof is drawn across a surface small particles thereof will be detached therefrom and transferred to said surface to form a coherent band of particles thereon, said particles comprising absorbent solid and pesticide.

The invention further provides a method of providing pesticidal protection on a surface, which comprises drawing across the surface a coherent solid source of pesticide comprising an absorbent solid impregnated with a pesticide, such that small particles from the source are detached therefrom and transferred to the surface to form a coherent band of particles thereon, said particles comprising absorbent solid and pesticide.

The solid source of pesticide is suitably in the form of a stick or a block, and is formulated to disintegrate in a controlled manner when moved in frictional contact with a surface to provide the band of particles on the surface. Because the transfer of particles to the surface occurs under the pressure of drawing the source across the surface, the particles adhere to the surface in a far more positive manner than could be achieved by the direct application of a powdered composition. Consequently, the pesticidallyactive band obtained is resistant to many environmental conditions which would reduce the effectiveness of only loosely adhering powders. Also, of course, application to vertical surfaces or undersurfaces (underneath shelving, for example) presents no problem.The present invention is especially useful inside buildings, especially domestic buildings.

The solid source of pesticide may be formed from a coherent solid carrier material which is capable of controlled disintegration into a powder when drawn across a surface. To that extent the source should be capable of behaving like blackboard writing chalk, and in fact the visual result of using a device in accordance with the present invention is normally similar to that achieved when writing with such chalk.

The carrier chosen should also be such that it will retain incorporated pesticide in both the coherent source and the transferred particles in a readily releasable manner. Carriers such as a hydrocarbon wax are capable of retaining many pesticides such as pyrethroid insecticides, but they do not do so in a readily releasable manner. The present invention depends on the ability of the carrier to provide a band of pesticide-containing particles which will release the pesticide when contacted by a pest, thereby killing the pest.For this reason a carrier such as ari absorbent inorganic solid or an absorbent gel in which the insecticide is held in a "reservoir" sense rather than being preferentially retained in solid solution (as would occur with lipophilic pesticides and hydrocarbon wax or a polyvinyl chloride matrix material) should be used in carrying out the present invention. The use of an absorbent inorganic mineral carrier is preferred. There is no difficulty in selecting suitable carriers on the basis of existing knowledge of the properties of the various pesticides which can be used, supplemented, if necessary, by routine trial.

One typical suitable carrier is calcium sulphate (gypsum), and a preferred way of forming a pesticide source for use in carrying out the present invention is to employ the kind of formulation and compaction techniques used to manufacture gypsum-based blackboard writing chalks. A block or stick thus made may be impregnated with an insecticide in liquid form, either as such or as a solution in an organic solvent.

Alternatively, the pesticide may be present in a slurry along with the carrier material prior to the formation of a block or stick. A device in accordance with the present invention is then formed by incorporating the impregnated block or stick in a holder or a removable wrapping, which can be manipulated by the user progressively to expose a marking portion for drawing across a surface.

The pesticide used can be selected from any suitable pesticide which is effective against the target pests.

The particular carrier or carriers used in forming the solid source will depend on the pesticide with which it is to be impregnated. In the case of pyrethroids, for example cypermethrin or permethrin, which are particularly preferred insecticides in view of their efficacy, a gypsum-based formulation has been found to be suitable. Such insecticides cannot be used efficiently on many surfaces when applied in a conventional manner in solution in an organic solvent due to absorption into the surface leading to loss of insecticidal activity.In the case of obviously absorbent surfaces, for example mortar, brickwork or cement rendering, this loss of activity occurs with all solutions capable of penetrating the surface, but with the pyrethroids and similar lipophilic compounds, a similar, and at first sight unexpected, problem arises with polymeric material surfaces such as polyvinyl chloride tiles and many painted surfaces due to the strong attraction these materials have for the insecticide which goes into solid solution in the material and is thereby rendered ineffective for its intended purpose. This problem can be overcome by applying the insecticide in a controlled manner by the method of the present invention.

Advantageously the solid source of pesticide is of elongated, eg. cylindrical, shape, and is housed in a similarly shaped container having a removable cap and means for propelling the stick forward progressively to expose a fresh portion thereof as it is gradually consumed in use. The container is conveniently made of a plastics material and the stick can be propelled forwardly either by pressing on a movable base plate or by means of a simple screw mechanism incorporated in the end of the container remote from the cap. The cap protects the exposed end of the stick when the device is not in use. With the cap in place the stick is effectively enclosed for storage. In a simple alternative the stick is wrapped with a protective material which can be unwound progres-sively to expose a fresh portion of the stick, and this wrapping will provide protection for the user's fingers to prevent contaminationthereof with pesticide, a simple cap being provided to put over the exposed end when not in use.

The following Examples illustrate the invention.

Example 1 Sticks of gypsum-based chalk were impregnated with acetone solutions of cypermethrin, the sticks being saturated and then dried, leaving 5% m/m cypermethrin content.

German cockroaches, Blattella germanica, were restrained within an 18cm diameter glass collar placed on a PVC floor tile, and the chalk was used to draw a 17cm diameter circle within the collar. This circle contained 1.6mg cypermethrin.

The times taken to knockdown 50% and 90% of the insects (KD50 and KD90) were recorded, and knockdown and kill were recorded after 24 and 72 hours. Fresh insects were supplied after 3,7 and 28 days. The results are given in Table 1.

TABLE 1 Days after 24 hours 72 hours Treatment KD50 KD90 knockdown kill knockdown kill 1 15 22 100 75 100 95 3 13 25 100 75 100 100 7 14 23 100 95 100 100 28 14 25 95 40 95 90 Example 2 Sticks of gypsum-based chalk were impregnated with acetone solutions of cypermethrin, the sticks being saturated therewith, and then dried to remove solvent and leave 2% (m/m) cypermethrin in the sticks.

The resulting sticks were then used to draw a continuous band round the perimeter of 30x30cm square samples of the test materials, these being vinyl (PVC-based) flooring tiles and concrete paving slabs. A solution of cypermethrin in hexane was applied by pipette to other samples of the same two test materials to affect a comparison with the chalk, sufficient of this solution being applied to give the same total amount of cypermethrin as on the corresponding chalk-treated surface.

The test insects used were the German cockroach (Blattella germanica) and the red ant (Myrmica rubra).

These were placed in clean 50 x 50 x 1 Ocm metal test trays. The cockroaches were provided with a shallow shelf located along one side of the test tray to act as a dark harbourage. The ants were provided with nest material (soil) placed in one corner of the tray.

The treated test panels were placed centrally in the test trays. Food and water for the insects were placed centrally in the middle of the test panel, within the perimeter of the insecticide treatment. The insects were allowed to forage naturally and the degree of knockdown of the insects was then observed at hourly intervals up to 5 hours (or 100% knockdown). Assessments of knockdown and of moribund or dead insects were made after 24 and 72 hours. Fresh batches of insects were exposed at various times up to one month after the initial assessment on the originally treated test panels in order to compare the persistence of the treatments.

Untreated test panels were used on each occasion to determine control knockdown and mortality.

The results of these tests are given in Tables 2 and 3. Each result is the mean from duplicate experiments. It can be seen from the results that the method according to the invention gave extremely effective control of the test species for the whole period of the test, one month. In contrast, application of cypermeth rin solutions gave very poor control even over short periods.

TABLE 2 Blatella germanica Days Deposit after %moribund at % dead at Product (mg cyper- treat- % knockdown at time (hours) time (hours) time (hours) Surface Tested methrin) ment 1 2 3 4 5 24 72 24 72 24 72 PVC Tile Chalk 0.66 0 35 90 100 - - 100 100 100 100 10 80 3 80 95 100 - - 100 100 100 100 15 85 7 85 100 - - - 100 100 100 100 40 80 14 60 80 90 95 95 100 100 100 100 15 65 31 60 95 100 - - 100 100 100 100 25 75 Solution 0.66 0 0 0 0 0 0 0 0 0 0 0 0 3 0 0 0 0 0 0 0 0 0 0 0 7 0 0 0 0 0 0 0 0 0 0 0 31 0 0 0 0 0 0 0 0 0 0 0 Paving Chalk 3.4 0 5 90 100 - - 100 100 100 100 15 70 Slab 3 95 95 100 - - 100 100 100 100 20 80 7 100 - - - - 100 100 100 100 40 100 14 80 95 100 - - 100 100 100 100 20 70 31 80 100 - - - 100 100 100 100 20 90 Solution 3.4 0 0 0 5 0 0 10 20 5 15 0 0 3 0 0 0 0 5 25 30 35 0 20 7 0 0 0 0 0 5 15 5 15 0 5 14 0 0 0 0 5 15 30 15 30 0 5 31 0 5 5 5 5 5 10 5 10 0 5 TABLE 3 Myrmica rubra Days Deposit after % Moribund % Dead Product (mg cyper- treat- % knockdown at time (hours) at 24 at 24 Surface Tested methrin) ment 1 2 3 4 5 hours hours PVC Tile Chalk 0.52 0 70 85 100 - - 100 100 3 100 - - - - 100 100 7 90 100 - - - 100 100 14 100 - - - - 100 100 31 50 75 85 85 85 100 100 Solution 0.52 0 0 0 0 0 0 5 0 3 0 0 0 0 0 10 5 7 0 0 5 5 5 5 5 14 0 0 0 0 0 5 5 31 0 0 0 0 0 0 0 Paving Chalk 2.5 0 20 80 90 95 100 100 95 3 100 - - - - 100 100 7 100 - - - - 100 100 14 100 - - - - 100 100 31 60 85 90 90 95 100 100 Solution 2.5 0 5 5 5 5 20 45 35 3 15 35 40 45 45 80 75 7 10 15 15 20 25 60 50 14 5 25 25 30 30 75 60 31 0 5 5 5 5 30 25

Claims (6)

1. A device suitable for providing pesticidal protection on a surface, which comprises a coherent solid source of pesticide comprising an absorbent solid impregnated with a pesticide, said source being contained within a wrapping or holder adapted to be manipulated progressively to expose said source, and said source .being such that when the so exposed part thereof is drawn across a surface small particles thereof will be detached therefrom and transferred to said surface to form a coherent band of particles thereon, said particles comprising absorbent solid and pesticide.

2. A device as claimed in claim 1, in which the solid source comprises an absorbent inorganic mineral.

3. A device as claimed in claim 2, in which the mineral is calcium sulphate.

4. A device as claimed in any one of claims 1 to 3, in which the pesticide is a pyrethroid insecticide.

5. A device as claimed in any one of claims 1 to 4, in which the solid source of pesticide is of elongated shape and is housed in a similarly shaped container having a removable cap and means for progressively propelling the stick forward.

6. A method of providing pesticidal protection on a surface, which comprises drawing across the surface a coherent solid source of pesticide comprising an absorbent solid impregnated with a pesticide, such that small particles from the source are detached therefrom and transferred to the surface to form a coherent band of particles thereon, said particles comprising absorbent solid and pesticide.